Due to, in part, recent changes in food culture and lifestyle, the number of people who needs dental treatment is on the increase, so that dental specialists frequently recommend for routine examination and early treatment of teeth. In most cases, treating the teeth involves X-ray imaging that examines the states of the tooth (the row of teeth) and the gum-ridge. In many conventional cases, the X-ray imaging is used to provide images of regional gum-ridges projected onto X-ray films. As alternative imaging techniques or techniques for parallel use with the projected images, apparatuses such as an X-ray CT scanner, a dental panoramic imaging apparatus are also used.
The X-ray CT scanner is used to apply the general CT imaging to the jaw portion. Hence the resolution of panoramic images reconstructed along the tooth row from acquired images by the scanner is not so high, which has limited its application to observing the entire tooth row.
On the other hand, the dental panoramic imaging apparatus comprises an X-ray source and an X-ray detector which are paired and arranged with the head of an object located therebetween. The paired members are moved around the head to acquire X-ray transmission date, and the data are used to produce panoramic images along a predetermined section along the tooth row. An example of this dental panoramic imaging apparatus is provided by a patent reference 1 listed below.
In the patent reference 1, exemplified is a digital type of panoramic imaging apparatus (the title of the invention is “digital panoramic X-ray imaging apparatus”). This panoramic imaging apparatus is provided with an X-ray source and an X-ray image detecting member arranged to be opposed each other with an object being examined located therebetween and rotation deriving means for rotating the X-ray source and the X-ray image detecting member as one unit. The X-ray source is provided with an X-ray tube and a collimator collimating X-rays radiated from the X-ray tube into slit-shaped beam X-rays. The X-ray image detecting member is provided with an X-ray detector, which is for example an X-ray CCD sensor, outputting digital electrical signals depending on incident X-ray intensity. Further, this panoramic imaging apparatus is provided with storage means for sequentially storing, as frame images, image information acquired by the X-ray detector and image processing means for panoramic images. The image processing means reads out the image information from the storage means at intervals in sequence, and, in relation to a direction along which images spatially are related among the sequential image information, the read-out image information is added on one another with a predetermined amount of shift. Thus the image processing means produces panoramic images of an arbitrary section in accordance with both the read-out intervals and the shift amounts. Accordingly, it is possible to provide, as diagnostic images, on the monitor of a personal computer or other devices, panoramic images of sections along patients' tooth rows.    [Patent reference 1] Japanese Patent Laid-open Publication No. 4-144548.